For many well-known reasons, aluminum is a good metal to include in cookware. It has good conductivity, lightweight, high latent energy and most alloys of aluminum can be readily formed into useful cookware shapes. Yet, most aluminum alloys are highly reactive and will react with cleaning detergents or food so the interior of cookware is often coated with a synthetic coating or bonded to stainless steel to provide an acceptable food preparation surface. The exterior is seldom left bare because of the soft and reactive nature of aluminum metal. Numerous paints and polymers and anodizing have been applied to protect aluminum while withstanding the rigors of wear and heat. Certain alloys of aluminum which contain high contents of other metals such as magnesium are much more resistant to chemical attack and mechanical wear but lack the ductility to be formed into useful shapes for cookware.